Technical Field of the Invention
The invention relates to the field of surgery, specifically to the field of installing bone implants having a head provided such as to receive a screw cap and, where appropriate, an accessory such as a link rod.
The invention relates specifically to a device for guiding a surgical instrument into position on the head of a bone anchor element having a tapped longitudinal recess intended for receiving a screw cap, said longitudinal recess leading into a transverse channel capable of receiving a link rod, the surgical instrument having one end for coupling to the head of said bone anchor element and a longitudinal channel.
State of the Art
The placement of a link rod in a head of a bone anchor element remains a rather complicated operation, since the rod is often offset (in terms of height and/or laterally) relative to the head of the bone anchor element. It is thus sometimes necessary to resort to complementary instruments in order to place the link rod in said head of the anchor element.
An example of such an instrument is described in patent application WO2005/099602, which discloses a surgical instrument intended for pushing a link rod into a spinal implant.
Also known from U.S. Pat. No. 6,440,133 is a surgical instrument for reducing a rod into a bone anchor element. The instrument includes an element that engages with the bone anchor element, said engaging element having a distal portion suitable for receiving a portion of the link rod, a reducing element arranged in a mobile fashion about the element engaging the bone anchor element and an actuator pivotably coupled with the element engaging the bone anchor element and pivotably coupled to the reducing element, the actuator making it possible to move the reducing element such that the latter comes into contact with the link rod and to move the latter towards the bone anchor element. The element engaging the bone anchor element includes a pair of flexible arms and a tab on the distal end of each of the flexible arms, each of said tabs defining a channel for receiving the link rod inside thereof.
However, said instruments each have a major defect which is the positioning on the head of the anchor element. Indeed, accurate positioning is necessary in order to ensure correct attachment between the instrument and the anchor element, which requires a careful gesture. The tissues surrounding the surgical incision actually impede access to the head of the anchor element and sometimes make it impossible to install these instruments given the constitution thereof. Placement is made even more difficult by the fact that the heads of the anchor elements used are mobile most of the time.